Effect Of Low-energy Electrons Research Articles

Quasirelativistic approach to many-channel electron scattering from atoms

A quasirelativistic approach to many-channel electron-atom scattering problems has been formulated. This method allows the author to take into account relativistic effects to almost the same extent as the more rigorous Dirac-Fock approach but is only slightly more complex than non-relativistic methods. It has been applied to study relativistic effects in low-energy electron scattering from alkali-like ions.

Resist Exposure Characteristics by a Focused Low Energy Electron Beam

Resist exposure characteristics by focused low energy electron beam (E‐beam) were studied from the viewpoint of nanometer scale pattern delineation. Single layer positive resist and multilayer negative resist were exposed with 1–20 kV electron beam. As the electron energy decreased, the penetration depth in a resist layer reduced, resulting in incomplete development of the single layer resist with a practical thickness. Resist sensitivity and proximity effect were considerably improved by decreasing the voltage. Fine patterning can be carried out in a multilayer resist process, because a top imaging layer can be very thin, but resist scums formed probably due to the charging‐up effect of low energy electrons. The charging‐up problem can be completely solved by applying a novel 2‐layer conducting resist system, and nanometer patterns as small as 40 nm were obtained with 2–5 kV exposure.

Non-adiabatic effects in low-energy electron scattering by molecules and molecular ions

A new method for the description of non-adiabatic effects in low-energy resonant electron scattering is developed. Analytic expressions for the elastic and inelastic cross sections are obtained within the framework of the oscillator model. The possibilities of the method are illustrated for resonant electron scattering by molecules possessing a virtual electronic level and by positive molecular ions.

A search for spin effects in low-energy electron scattering from optically active camphor

A search for spin effects in low-energy electron scattering from optically active camphor

A search for spin effects in low-energy electron scattering from optically active camphor

It was recently suggested that spin polarisation effects might occur in electron scattering from optically active molecules due to 'parity violation', i.e. originating from the lack of inversion symmetry in the target. This suggestion has been put to an experimental test. Elastic scattering experimentals were performed on camphor at 25 eV in the angular range between 40 degrees and 70 degrees . The polarisation is found to be less than the error margin of 0.5% (two standard deviations).

Adsorption states and Ga depletion during oxygen adsorption on clean polar GaAs surfaces

Ultraviolet photoelectron spectroscopy (UPS), thermal desorption spectroscopy (TDS) and Auger (AES) measurements were used to study oxygen adsorption on sputtered an annealed GaAs(111)Ga, (1̄1̄1̄)As, and (100) surfaces. Two forms of adsorbed oxygen are seen in UPS. One of them is associatively bound and desorbs at 400–550 K mainly as molecular O 2. It is most probably bound to surface As atoms as indicated by the small amounts of AsO which desorb simultaneously. The second form is atomic oxygen bound in an oxidic environment. It desorbs at 720–850 K in the form of Ga 2O. Electron irradiation of the associatively bound oxygen transforms it into the oxidic form. This explains the mechanism of the known stimulating effect of low energy electrons on the oxidation of these surfaces. During oxygen exposure a Ga depletion occurs at the surface which indicates that oxygen adsorption is a more complex phenomenon then is usually assumed. The following model for oxygen adsorption is proposed: oxygen impinges on the surface, removes Ga atoms and thus creates sites which are capable of adsorbing molecular oxygen on As atoms of the second layer and are surrounded by Ga atoms of the first layer. This molecular oxygen is stable and simultaneously forms the precursor state for the dissociation to the oxidic form.

Relativistic effects in low energy electron scattering from atoms

Abstract Recent relativistic calculations on low energy elastic scattering of electrons from atoms are reviewed. Two aspects are emphasized : mathematical transformations and numerical methods used in the solution of the Dirac equation and the summation of the partial wave series ; and the results of relativistic calculations, in particular the behaviour of the cross sections and spin polarizations for different atoms, different energies of the incident electron, and in different approximations. The effects of the screening of the nucleus by the atomic electrons, electron exchange (including the use of approximate exchange potentials) and the distortion of the atom by the incident electron are discussed. Detailed results for cross sections and spin polarizations are given for mercury and the inert gases. The differences arising from use of the Dirac equation instead of the Schrodinger equation are considered.

Low-Energy Electron Interaction with Coadsorbates on Tungsten

The effect of low-energy electrons (20–300 eV) impinging on cesium, mercury, and oxygen adsorbed on clean and oxygenated tungsten has been studied by field-emission techniques. Desorption cross sections were determined from the work-function changes and the known relationships between work function and coverage for the various systems studied. For cesium on clean tungsten and for mercury on both clean and oxygenated tungsten, the cross sections are less than 10−21 cm2, the minimum level of sensitivity for these experiments. Cesium is desorbed from an oxygenated tungsten surface by the impact of 250 eV electrons without disturbing the underlying chemisorbed oxygen layer. Cross sections for the desorption of cesium from oxygenated tungsten increase with increasing cesium coverage to a maximum of 8×10−20 cm2, and are insensitive to the amount of underlying oxygen. These results suggest that an important change in the character of the surface bond is effected by the underlying oxygen layer, in particular, a greater localization of the bonding electrons in the cesium-oxygen bond as compared to the cesium-tungsten bond.

Production and Effects of Low-Energy Electrons in Helium

Production and Effects of Low-Energy Electrons in Helium